Direct reduction of iron oxide containing ore in fine, lump and pellet form is well known in the metallurgical literature. In general, such processes have evolved for the purpose of directly reducing the iron oxide containing ore in a solid-state form to form elemental iron, commonly known as direct reduced iron, or "DRI." DRI may be used as substitute for steel scrap. Recent increases in steel scrap prices are indicative of future trends which is a result of the continuing decline in availability of top grades of steel scrap. Accordingly, DRI is being viewed as a reasonably priced substitute for basic iron units. DRI is easily melted in an electric arc furnace or blast furnace to produce high quality steel, having a low percentage of residual elements or gangue. By using DRI as a complement to the furnace charge, DRI compensates for the negative effects of certain types low grade steel scrap.
An added advantage of DRI in steel making processes is that coke may be replaced by less costly coal to supply carbon for fuel and to serve as a chemical reductant in converting the iron ore into elemental iron to form DRI.
The preparation of elemental iron from iron-bearing material such as iron-bearing ores has presented many difficulties. Generally, natural ore fines are too coarse for pelletization and too fine for iron making processes using conventional technology. For a more detailed discussion of various known processes and apparatus for metal oxide recovery reference is made to U.S. Pat. Nos. 5,186,741; 4,701,214; 4,251,267; 3,452,972 and 2,793,109 all of which are hereby fully incorporated by reference.
The present invention is directed to a process for treating iron-bearing material. As used herein, the term "iron-bearing material" specifically refers to virgin, i.e., untreated or unprocessed, iron oxide concentrates and natural iron ore fines such as hematite, limonite, magnetite, taconite, siderite, pyrites and chromite as opposed to steel mill waste, electric arc furnace dust, rolling mill scale, or the like, collected as a result of normal steel making operations.
It will be appreciated that there is a significant need for an improved process for refining iron-bearing material to elemental iron. An object of the present invention is to provide a process for agglomerating a mixture of iron-bearing material and a carbonaceous material to form green compacts for refinement of iron from the iron-bearing materials. The formation of compacts may be accomplished using an organic binder if the carbonaceous material contains less than about 20 wt % volatile matter or they may be formed without an organic binder if the carbonaceous material contains more than about 20 wt % volatile matter. Yet another object of the present invention is to provide a process for refining iron-bearing material to convert iron-bearing material to iron that is simple and economical. The economic advantage may be manifested in reduced transportation costs and reduced melting costs at the point of steel making.